Okay, I haven't been playing MR very long, but I think that at least one combination of the following challenges below is unprecedented and possible. Here goes:
1)beat the game with a single spellcaster without using magic
2)beat the game unequipped
3)beat the game dropping every item you find except for necessary items
4)defeat murkon being level 0 upon engaging battle with him
5)beat the game parrying for the first 10 turns of every battle (including the leviathin, Murkon, the grim reaper, the whole chebang)
6)cover every open square of every level before beating the game
7)beat the game without resting at inns, ever
8)beat the game with the only town that you have been in being Perinn
9)beat the game without a character dying, ever (not recommended to be attempted in conjunction with number
10)beat the game without using any free points
11)beat the game using only one character